GLACIERS OF ALASKA 21 Spurr, and Brooks had partly shown its limits,1 before the publication of Brooks's more complete 1906 map. From this map it may be seen that the Pacific Mountains not only contain more and larger glaciers than the Arctic Rocky Mountains at present, but that the same was true at the stage of maximum glaciation. In the Yukon and Kuskokwim. valleys and on the Arctic slope the glaciers may have extended short distances farther than the limits shown, for the till might be buried beneath outwash and recent alluvium, but the extension would be slight. On the Pacific Coast little is known of the seaward limits of the extended glaciers. EXTENT AND IMPORTANCE OF ALASKAN GLACIERS The preceding brief outline of our knowledge of the present-day glaciers of Alaska and of the former extent of glaciers in that territory is probably not complete, but it suffices to show two facts with striking clearness,—first that there is an enormous number of glaciers in a very large area, and secondly that much remains to be done on the study of Alaskan glaciers and glaciation before we can claim to have more than the merest reconnaissance knowledge of the phenomena of this great field. When we consider the remoteness of the region, the inaccessibility of many parts of it, and the brief time in which systematic exploration has been in progress, the results already obtained in the study of the Alaskan glaciers and glacial phenomena are noteworthy, especially as the glacial study has often been but a minor incident in other work. To the United States Geological Survey, and especially to the Alaskan division, under the direction of Alfred H. Brooks, the major credit for these results is due. From our outline of the present knowledge of Alaskan glaciers it is evident that it would be possible to give, even now, a much greater body of space to the subject, for in the reports to which reference has been made there are many important details and descriptions of individual glaciers. This has not been done, however, because even with the fullest abstracts of all reports, the discussion of Alaskan glaciers and glaciation would necessarily be most incomplete, with great and important gaps. It is our hope, in time, after some years of systematic work in the various glacier fields, to return to this subject and'to present an outline description and discussion of living glaciers and glacial phenomena of Alaska, on the basis of wider observation. For scores of years, however, it is not to be expected that a complete account of the region will be possible. At present we do not know even the approximate number of Alaskan glaciers. There are several hundred to which names have been given; there are dozens which are tidal and other dozens which reach almost to the sea; scores reach beyond the mountain base and expand in piedmont bulbs; and scores and probably hundreds of glaciers have a length of from ten to fifty miles or more. In all, there are sdme thousands of glaciers in the Alaskan mountains only a small percentage of which have received names, and many of which have never even been seen. The Alaskan region is one of the most wonderful regions of glaciation in the world, both from the standpoint of number and size of its glaciers, and from the extent and variety of i Hayes, C. W., Nat Geog. Mag., Vol. IV, 1892, Pis. XIX and XX. Spuir, J. E., 18th Ann. Kept., U. S. GeoL Survey, Part IE, 1897, PI. XXXVH Brooks, A. H., 20th Ann. Rept., U. S. Geol. Survey, Part HI, 1900, Map 25; 21st Ann. Kept., U. S. Geol. Survey, Part U, 1901, PL XLVEL.